Wet crushing process and crusher for implementing such process

ABSTRACT

A grinder for use in wet grinding having a roller or wheel rolling on a circular track and elastically pressed thereon. The materials to be ground are subjected to several layer on bed grinding operations to enable the rational utilization of this type of grinder. During the time between two successive grinding operations in the grinder, water or another liquid is introduced by nozzles to the materials. The materials are drained and/or dried by a screen so as to reduce water content to below 20% in volume.

TECHNICAL FIELD

The present invention relates to wet crushing and to crushers comprisingat least one roller travelling over a circular track and elasticallypressed against the latter.

BACKGROUND ART

Known crushers of the type defined above, a vertical crusher or ringcrusher, in which a multi-granular layer of materials for crushing iscompressed between the roller and the track with sufficient pressure tocrush the grains and cause their fragmentation to smaller grains, arenot suited to wet crushing as an excessive water content in thematerials for crushing reduces their efficiency. In wet crushing, thematerials for crushing generally have a water content of 10% to 60% byweight, with an average of 30%, which is incompatible with good crushingefficiency.

The object of the present invention is to permit the rational use ofcrushers of this type for wet crushing.

SUMMARY OF THE INVENTION

The process according to the present invention includes in subjectingthe materials for crushing to several crushing operations by crushing ina layer or bed of materials and, during their dwell time in the crushingapparatus, and between two successive crushing operations, in addingwater or another liquid to the materials to re-expand the layer ofmaterials and to enable the progress of the materials through thecrushing apparatus to be controlled and, possibly, to enable their grainsize grading to be ensured, and then in draining the materials and/orremoving moisture therefrom so as to reduce their water content to lessthan 20% by volume. The draining and moisture removal operations arecarried out inside the crushing apparatus, which is arranged for thispurpose, which makes it possible to achieve a considerable reduction inthe cost of the plant by avoiding the use of auxiliary apparatus andmeans of transport between the different apparatus.

For the purpose of implementing the invention, use will be made of acrusher comprising a circular track, fictitiously divided into severaltrack elements, or circular tracks, spaced apart from one another, wherethe successive crushing operations will be carried out, means fortransferring the materials from one track or track element to the next,means for projecting water or another liquid onto the materials duringtheir transfer from one track or track element to the next, and meanssuitable for ensuring the draining of the materials and/or removal ofmoisture therefrom prior to their next passage beneath the roller. In aring crusher having a horizontal axis, the tracks will be disposed sideby side.

The addition of water or of another liquid to the materials after eachcrushing operation makes it possible, on one hand, to improve the flowof the materials and their distribution in a layer of uniform thicknessover the track, and, on the other hand, to remove the fine particlesimmediately after their production, which makes the subsequent crushingoperations more efficient.

The water or any other liquid can be projected onto the materials whenthey are still on the track, for example by means of nozzles suppliedunder pressure which then constitute one of the means for transferringthe materials from one track or track element to the next. Inparticular, when the crusher is of the rotary ring type and is driven inrotation at a speed greater than the critical speed so that thecentrifugal force is sufficient to maintain a layer of materials overthe entire periphery of the track provided on the ring, use can be madeof nozzles placed inside the ring, in its upper portion and on therising side, and the jets of which will be directed towards the track todetach the materials; the action of the jets can be supplemented by thatof a scraper. Moisture removal can be effected through the action of thecentrifugal force in the portion of the track located upstream of thecrushing roller. A pre-compression roller can be provided on the track,immediately ahead of the crushing roller, to ensure complementarymoisture removal by pressure.

According to a preferred form of embodiment of the invention, thecrusher is of the rotary ring type and the material feed devicecomprises one or more baffle or deflecting plates arranged so as tointercept the materials detached from the track provided inside the ringand orientated so as to deflect them in a direction having a componentparallel to the axis of the ring; additional water spraying means can beprovided above the deflecting plate or plates to facilitate the flow ofthe materials. Alternatively, the deflecting plate or plates can beporous, and water or another liquid can be injected through the plate(s)to create a liquid film facilitating the flow of the materials. Thedeflecting plate or plates can comprise an upper screening surface andmeans for collecting and discharging the water and the fine crushedproducts that pass through this surface; they then constitute a meansfor draining the coarse materials. They can be flat or curved, and eachplate will be orientatable about a horizontal axis, and possiblyinclinable about a vertical axis, so as to be able to adjust the feedingspeed of the materials for crushing and choose the point at which thematerials deflected by the plate(s) fall back onto the track. Theremoval of moisture from the materials is carried out, through theaction of the centrifugal force, in the area of the track locatedbetween the point at which the materials deflected by the deflectingplate or plates fall back onto the track and the roller. Preferably,this area will have an angular extent of at least 30°.

In the event of the track being formed inside a drum with a horizontalaxis and of supply and discharge areas being arranged on either side ofthe track, drainage means can be provided in these areas to facilitatedischarge of the water. For the same purpose, when the track isconstituted by protection plates resting on the shell of the drum, whichis generally the case, drainage means can be provided under the plates,in the crushing area. A grooved roller can also be used. At its ends,the drum will be provided with annular barrier-forming rims the insidediameter of which will be chosen to retain the material within thesupply and discharge areas, respectively, while, at the same time,possibly enabling the water to be discharged by overflowing. These rimscan be designed in such a way that is possible to change their insidediameter in order to adjust their height (radial dimension). Thematerials retained by these rims form, at least at the crushing area, abank that prevents the materials compressed between the roller and thetrack from being expelled laterally by the pressure while, at the sametime, enabling the water to be discharged partially through the saidbank, if the supply area, or discharge area, respectively, is providedwith drainage means, and partially by overflowing the bank.

A rotary screen, having a horizontal axis, can be placed at the crusheroutput to sort the crushed products. The rejects of the rotary screencan be returned to the track or to the crusher input by an internalrecycling device comprising a conduit disposed inside the crusher,transversely to the track, means for supplying the said conduit with thescreen rejects and, possibly, means for facilitating the flow of therejects through the conduit. The screen can be integral with the body ofthe crusher or supported and driven by individual means. Water injectionmeans can be provided in the rotary screen to facilitate discharge ofthe crushed products and possibly reconstitute with them a pulp of acomposition suitable for subsequent processing.

According to a first alternative form of embodiment, the crushercomprises two tracks spaced axially from one another inside a drum witha horizontal axis, two rollers, each suitable for travelling over atrack, means for bringing the materials for crushing into the drum,between the two tracks, and means for discharging the crushed materialsat the two ends of the drum.

According to another alternative form of embodiment, the crushercomprises several tracks spaced axially from one another inside a drumwith a horizontal axis, several rollers, each suitable for travellingover a track, means for introducing the materials for crushing into thedrum at one of its ends, means for transferring the materials from onetrack to the next and means for discharging the crushed materials at theother end of the drum, drainage means for discharging the water beingprovided between the tracks.

BRIEF DESCRIPTION OF THE DRAWINGS

The description that follows makes reference to the accompanyingdrawings which show, by way of non-limitative examples, a preferred formof embodiment of the invention and two alternative forms of embodiment.In these drawings

FIG. 1 is a diagrammatic representation, in transverse cross-section, ofa crusher designed according to the invention;

FIG. 2 is a cross-section along line A—A′ of FIG. 1, the roller and theinternal equipment of the crusher being shown in elevation;

FIG. 3 is a view, analogous to that of FIG. 1, of an alternative form ofembodiment; and

FIG. 4 is a view, analogous to that of FIG. 2, of another alternativeform of embodiment.

DETAILED DESCRIPTION OF THE INVENTION

The crusher shown in FIGS. 1 and 2 is a ring type crusher constituted bya drum 2 having a horizontal axis supported by one or more pairs of padsor skids 6 permitting its rotation about its axis. The drum is driven inrotation in the direction of arrow R by conventional means, not shown.It is constituted by a shell the median part of which is internally cladwith wear plates and forms a ring bearing the crushing track.

A roller 4 is placed inside the shell so as to travel over track 18 whenthe drum is driven in rotation. The roller is integral with a shaftparallel to the axis of the drum and the ends of which, which arelocated outside the drum, are mounted in bearings capable of moving inslide ways or supported by pivoting arms; springs or jacks act on thebearings so as to press the roller against the track with apredetermined, adjustable force. This arrangement is conventional, andthe shaft and the bearings have been omitted from the drawings to avoidimpairing their legibility. The roller can be idle or driven in rotationby a geared motor.

In the form of embodiment shown in FIGS. 1 and 2, the surface of thetrack and the peripheral surface of the roller are cylindrical, but theycould be frustoconical or cylindroconical, or formed of several portionshaving different diameters, as described, for example, in U.S. Pat. No.9,109,788 in the name of the applicant.

The materials for crushing are introduced into the drum via a chute 20disposed at one end of the drum; at the other end, where the crushedmaterials are discharged, the shell is prolonged by a cylindrical screen14 which is surrounded by a collector means 15. Nozzles 24, placedinside the screen 14, enable the crushed materials to be sprayed toimprove screening and possibly produce a pulp of suitable compositionfor subsequent processing.

A chute 16, disposed in the drum, transversely to the track, with anappropriate slope, enables the screen rejects to be returned to thesupply area of the crusher. This chute is supplied at one of its ends,for example by a device for scraping the inner surface of the screen:water injection means can be provided to facilitate the flow of therejects along the chute.

The crusher is equipped with a device for the stepwise feeding of thematerials, constituted by water injection nozzles 12 and a screen 8.

Nozzles 12, mounted on a supply pipe, not shown, are disposed in such away that their jets are directed towards the surface of the track todetach the layer of materials therefrom. The action of the nozzles couldpossibly be assisted by a scraper, parallel to the axis of the drum anddisposed close to the surface of the track, as described in U.S. Pat.No. 9,109,788 in the name of the applicant; preferably, the edge of thescraper will not be in contact with the surface of the track, but at ashort distance therefrom, to reduce wear.

Screen 8 is constituted by a flat or curved grid and a collectingrecipient. It is mounted on a support 26 so as to be able to pivot abouta vertical or inclined axis 28 thanks to a connecting rod and jacksystem, not shown. It can possibly be mounted to as to be able to pivotabout a horizontal axis in order for it to be possible to change itsangle of inclination. A chute 17 serves to supply to screen 14 the waterand the fine crushed materials collected in the collector means ofscreen 8. Means can be provided for transmitting oscillations orvibrations to screen 8.

As seen in transverse cross-section, the inside of the crusher can bedivided into five clearly defined areas: a crushing area BC, a raisingarea CD, a scraping area DE, a feed and drainage area EF and a moistureremoval area FB.

In longitudinal cross-section, the inside of the crusher can be dividedinto three areas: a supply area 30, a crushing area 31 and a dischargearea 32. The inner cladding of the supply and/or discharge areas can bedesigned to enable the water to be discharged by drainage.

In operation, the materials for crushing are introduced via chute 20into the supply area 30 of the drum and there forms in this area a layerof materials the progress of which, parallel to the axis, is controlledby the feed device. A rim 21 of drum 2, the inside diameter of which issubstantially equal to that of the layer of materials present on thetrack forms a barrier permitting the formation of the layer. The speedof rotation of the drum is greater than critical speed, so that thelayer of materials is retained on the wall of the drum by centrifugalforce, over its entire periphery. A part of the water contained in thematerials is possibly discharged in this area by drainage.

To take an elementary volume of the layer of materials present on thetrack, for example at the upstream end of crushing area BC, this volumeis first subjected to crushing by compression between roller 4 and track18 and then, remaining pressed against the track by centrifugal force,it is raised to the scraping area, where it is detached from the trackand broken up by the jets of water from nozzles 12. The grains ofmaterial forming this elementary volume then drop onto screen 8, wherethe water and the grains that are sufficiently fine pass through thescreening surface, are collected by the collector means and conveyed torotary screen 14 via chute 17, while the coarser grains slide along thescreen.

The orientation and angle of inclination of the screen are such that thedownward movement of the materials over the screen is accompanied by amovement that is parallel to the axis of the drum and the length ofwhich is equal to a fraction of the width of the track. By adjusting theorientation of the screen, it is possible to control the progress of thematerials to compel them to undergo several cycles of crushing beforebeing discharged from the crusher. The action of the screen as anelement of the stepwise feed device is comparable with that of thedeflecting plates in the crusher that is the object of above-mentionedU.S. Pat. No. 9,109,788.

The drained materials drop from the screen onto the track, where theyreconstitute a layer from which moisture is removed, through the actionof centrifugal force, in area FB, between the point at which they dropand crushing area BC. To permit satisfactory moisture removal, theangular extent of area FB must be at least 30°; the relative positionsof roller 4 and screen 8 will be chosen to meet this requirement.

The centrifugal force also produces, in the moisture removal area, agrain size grading of the solid particles, which improves the work ofthe crusher.

Upon leaving the moisture removal area, the materials enter the crushingarea to begin a new cycle. The materials thus pass several times betweenthe roller and the track before reaching the edge of the track adjacentto discharge area 32, the number of crushing cycles being equal to theratio of the progress per turn, or step, to the width of the track. Itcan be considered that each fraction of the track having a width equalto one step forms a fictitious track element.

When the materials arrive in the discharge area, they are deflected byscreen 8 towards rotary screen 14. The grains of crushed materials thedimensions of which are greater than those of the apertures in screen 14are returned to the input of the crusher by internal recycling device16. The fine grains and the water are discharged at 22.

On the output side, the drum is provided with a rim 23, the insidediameter is approximately equal to that of the layer of materials. Thisrim permits the formation, in discharge area 32, of a bank of materialswhich prevents an excessive quantity of materials from being entrainedby the water when the fluidity of the layer of the materials present onthe track is excessive, and which opposes expulsion of the materialsthrough the effect of the pressure of the roller in the crushing area.Rims 21 and 23 can be designed in such a way that their inside diametercan be changed to adapt it to the nature and/or the behaviour of thecrushed materials; they can, for example, be formed of exchangeablesegments or rings.

As shown in FIG. 3, a pre-compression roller 5 can be placed on thetrack just before the crushing area to supplement removal of moisturefrom the layer of materials and prevent the water discharged by moistureremoval above the layer of materials from reaching the crushing roller.Known means will be used to adjust the pressure exerted by roller 5 onthe layer of materials.

Steps can be taken to facilitate the discharge of water in the crushingarea: grooving the roller, providing drainage means under the protectionplates of the track, etc.

Instead of being integral with drum 2, screen 14 could be supported anddriven independently. It could, for example, rotate at a speed belowcritical speed and be equipped with raising means or scoops enabling therecycling chute 16 to be supplied with the rejects.

Instead of comprising a single track fictitiously divided into trackelements, the crusher could comprise several tracks axially spaced apartfrom one another along the drum, drainage andlor moisture removal meansbeing provided between the tracks.

The crusher shown in FIG. 4 comprises two tracks, 18′ and 18″, disposedon either side of the median plane of the drum and axially spaced apartfrom one another, and two rollers 4′ and 4″ each travelling over atrack.

The materials for crushing are brought via a chute, or any other supplymeans, not shown, into the space between the two tracks, where theyform, through the effect of centrifugal force, a layer that is broughtonto the two tracks by feed devices.

Each track is equipped with a step wise feed device, for example of thesame type as that of the crusher of FIGS. 1 and 2, which ensures thedisplacement of the materials from the middle towards each end of thedrum. These devices are not shown in FIG. 4.

The shell of the drum is prolonged at each of its ends by a cylindricalscreen 14′, 14″ equipped with water injection nozzles 24′, 24″.Collector means 15′, 15″ collect the water and the fine grains that havepassed through the screens, and two recycling devices, 16′, 16″ enablethe screen rejects to be sent back to the median area of the drum.

Each half of the crusher in FIG. 4 operates like the crusher in FIGS. 1and 2. For the same production capacity, this construction enables thewidth of the track to be divided by two, which facilitates discharge ofthe water in the moisture removal area.

Many changes may be made to the forms of embodiment described throughthe use of equivalent technical means and it is clearly understood thatsuch changes fall within the scope of the invention.

What is claimed is:
 1. A crusher apparatus comprising: a circular trackfictitiously divisible into several elements where successive crushingoperations can occur; a crushing roller travelable over said circulartrack and elastically compressible against said circular track; transfermeans cooperative with said circular track for transferring materialfrom one element to a next element, said transfer means comprising aprojecting means for projecting a liquid onto the material during thetransfer of material from said one element to said next element; anddrain means cooperative with said circular track for removing moisturefrom the material prior to passing the material between said crushingroller and said circular track.
 2. The apparatus of claim 1, saidprojecting means comprising a plurality of nozzles capable of projectingliquid under pressure onto the material on said circular track.
 3. Theapparatus of claim 2, further comprising: a rotary ring having ahorizontal axis, said crushing roller positioned interior of said rotaryring, said circular track being an inner face of said rotary ring, saidcrushing roller rollable over said inner face; transport meanscooperative with said rotary ring for transporting material for crushingonto said circular track; feeding means cooperative with said rotaryring for axially displacing material detached from said circular trackand returning the displaced material toward said crushing roller forcrushing; and discharge means cooperative with said circular track fordischarging crushed material, said plurality of nozzles being positionedwithin an upper portion of said rotary ring, said plurality of nozzleseach having a jet directed toward said circular track.
 4. The apparatusof claim 3, said transfer means further comprising: a scraper positionedtransversely to said circular track downstream of said plurality ofnozzles.
 5. The apparatus of claim 3, said feeding means comprising: adeflecting plate positioned in said rotary ring so as to interceptmaterial detached from said circular track, said deflecting plate beingpermeable.
 6. The apparatus of claim 5, said deflecting plate comprisinga flat or curved screen, said discharge means for collecting the liquidand for discharging material passed through said screen.
 7. Theapparatus of claim 5, said deflecting plate being angularly adjustableabout a substantially vertical axis.
 8. The apparatus of claim 5, saiddeflecting plate being angularly adjustable about a substantiallyhorizontal axis.
 9. The apparatus of claim 3, said circular trackcomprising a first element cooperative with said drain means, said firstelement being between a point where the material detached by saidfeeding means fall back to said circular track and a point where saidcrushing roller contacts said circular track, said first element havingan angular extent around said circular track of at least 30°.
 10. Theapparatus of claim 3, further comprising: a rotary screen alignedcoaxially with and on one side of said rotary ring.
 11. The apparatus ofclaim 10, further comprising: recycling means cooperative with saidrotary screen for transporting a portion of material in said rotaryscreen toward said crushing roller.
 12. The apparatus of claim 1, saiddrain means comprising: a pre-compression roller positioned against saidcircular track adjacent said crushing roller so as to remove moisturefrom the material by pressure.
 13. The apparatus of claim 1, furthercomprising: a drum having a horizontal axis divided into a supply areaand a crushing area and a discharge area, said circular track beingpositioned in said crushing area, said discharge area having said drainmeans therein.
 14. The apparatus of claim 13, said drum having anannular rim on opposite sides thereof.
 15. The apparatus of claim 14,said annular rim having an adjustable inner diameter.
 16. The apparatusof claim 1, said circular track comprising a first track and a secondtrack spaced axially from each other, said first track and said secondtrack positioned within a drum having a horizontal axis, said crushingroller comprising a first roller and a second roller each travelablerespectively over said first track and said second track, said drumhaving a first rotary screen positioned on one side of said drum and asecond rotary screen positioned on an opposite side of said drum, theapparatus further comprising: transport means cooperative with said drumfor moving the materials into said drum between said first track andsaid second track.
 17. The apparatus of claim 1, said circular trackcomprising several tracks spaced axially from one another within a drum,said drum having a horizontal axis, said crushing roller comprisingseveral rollers travelable respectively over said several tracks, saidtransfer means for transferring the material from one track to anothertrack of said several tracks, said drain means being positioned betweenadjacent tracks of said several tracks, the apparatus furthercomprising: transport means cooperative with said drum for moving thematerial into the drum, said transport means positioned at one end ofsaid drum; and discharge means positioned at an opposite end of saiddrum for discharging crushed material from said drum.
 18. The apparatusof claim 1, said crushing roller having a grooved peripheral surface.